Question 1110285
Prom tickets beforehand were $31 and at the door they were $40 a total of 200 tickets were sold. Total money collected for both was 6,641.00 
- How many tickets were sold at the door?

Let beforehand tickets sold be x
door tickets sold be y
x+y = 200................1

Value equation
31x+40y = 6641...........2

Multiply (1) by 31
31x+31y=6200
31x+40y = 6641

subtract
-9y = -441
y =49

you can calculate x  by plugging y